Interatomic

A Rust library for calculating interatomic interactions such as van der Waals, electrostatics, and other two-body or many-body potentials. Designed for molecular simulations with support for SIMD acceleration and spline tabulation.

Features

• Two-body potentials: Lennard-Jones, Mie, Morse, WCA, FENE, Harmonic, Hard Sphere, Ashbaugh-Hatch, Kim-Hummer, Urey-Bradley
• Electrostatics: Ion-ion interactions with Plain Coulomb, Yukawa, and polarization schemes (via coulomb crate)
• Three-body potentials: Harmonic and Cosine angle/torsion potentials
• Four-body potentials: Harmonic and Periodic dihedral potentials
• Combination rules: Lorentz-Berthelot, geometric, arithmetic, and Fender-Halsey mixing rules
• Spline tabulation: Andrea spline for fast potential evaluation
• SIMD support: Vectorized operations via the wide crate
• Serialization: Optional serde support for all potentials

Installation

Add to your Cargo.toml:

[dependencies]
interatomic = "0.3"

With serde support:

[dependencies]
interatomic = { version = "0.3", features = ["serde"] }

Usage

Two-body Potentials

use interatomic::twobody::{LennardJones, IsotropicTwobodyEnergy};

let epsilon = 1.5;  // depth of potential well (kJ/mol)
let sigma = 2.0;    // distance at which potential is zero (Å)
let lj = LennardJones::new(epsilon, sigma);

let r_squared = 4.0;  // squared distance (Ų)
let energy = lj.isotropic_twobody_energy(r_squared);

Combining Potentials

Potentials can be combined using static or dynamic dispatch:

use interatomic::twobody::{LennardJones, Harmonic, Combined, IsotropicTwobodyEnergy};

// Static dispatch
let lj = LennardJones::new(1.0, 2.0);
let harmonic = Harmonic::new(0.0, 10.0);
let combined = Combined::new(lj, harmonic);

// Dynamic dispatch with Box
let pot1 = Box::new(LennardJones::new(1.0, 2.0)) as Box<dyn IsotropicTwobodyEnergy>;
let pot2 = Box::new(Harmonic::new(0.0, 10.0)) as Box<dyn IsotropicTwobodyEnergy>;
let combined = pot1 + pot2;

Electrostatics

use interatomic::ELECTRIC_PREFACTOR;

let z1 = 1.0;                    // charge number
let z2 = -1.0;                   // charge number
let r = 7.0;                     // separation (Å)
let rel_dielectric = 80.0;       // relative dielectric constant
let energy = ELECTRIC_PREFACTOR * z1 * z2 / (rel_dielectric * r);  // kJ/mol

Combination Rules

use interatomic::CombinationRule;

let rule = CombinationRule::LorentzBerthelot;
let (eps1, eps2) = (1.0, 2.0);
let (sig1, sig2) = (3.0, 4.0);
let (epsilon_mixed, sigma_mixed) = rule.mix((eps1, eps2), (sig1, sig2));

Spline Tabulation

For expensive potentials, spline tabulation can significantly improve performance:

use interatomic::twobody::{LennardJones, SplinedPotential, SplineConfig, IsotropicTwobodyEnergy};

let lj = LennardJones::new(1.0, 3.0);
let config = SplineConfig::default();
let cutoff = 12.0;

let splined = SplinedPotential::with_cutoff(&lj, cutoff, config);
let energy = splined.isotropic_twobody_energy(9.0);

Units

The library uses:

• Distance: Ångström (Å)
• Energy: kJ/mol

License

Licensed under the Apache License, Version 2.0. See LICENSE for details.